The central goal of this study is to define the mechanisms that control the age associated changes of the T cell repertoire. A dramatic example of the B cell changes that occur frequently with age is the occurrence of so-called Benign B cell Monoconal Gammapathy (BBMG). Prelimary results suggest that the investigators have found what could be the T cell equivalent to BBMG. The overall goal of this proposal is to investigate the nature and biological significance of CD8+ CD28-clonal expansions which occur in elderly humans Progress report and summary of findings: Data collected explains the presence of CD45RA+ T-cells in the elderly, shed light into the filogenetic origin of CD28-CD8+ T-cells and suggest a role for these cells in the immune senescence process.